1. Field of the Invention
The invention relates to a device for the paper transport in an office machine, in particular in a matrix printer, with a print-support surface supported in side plates for individual sheets or, respectively, endless webs transportable with a friction drive, as well as for edge-perforated endless webs with tractors provided in pairs in a pull or push operation.
2. Brief Description of the Background of the Invention Including Prior Art
Such paper transport devices are essentially required for two, in general differing, kinds of paper. On the one hand, individual sheets or, respectively, endless webs without perforation are transported and, on the other hand, tractors are employed which, as their name indicates, operate in pull operation and are provided as mounting devices. Depending on whether the operation is with individual sheets, i.e. non-perforated endless webs, or with edge-perforated endless webs, correspondingly, a special device for the transport of the paper is required.
The use of a friction drive with a print roller pair or of a tractor with a tractor pair depends further on whether the print-support surface is provided as a print roller or as a spatially fixedly disposed print bar.
It is known from the U.S. Pat. No. 2,140,028 to provide both a friction drive as well as tractors for a paper transport device. The known device however does not allow to employ the tractor, in addition to the pull operation, also for the push operation. This means that the conventional device is not simultaneously suitable for several kinds of paper. Under "simultaneously suitable" is understood in this context that an operation with differing kinds of papers can be performed in an advantageous way where, respectively, one or the other kind of paper is available in a waiting position, i.e. placed in the paper transport device.